1. Field of the Invention
The invention relates to a light-emitting diode having an omnidirectional reflector (ODR), and more particularly, to a light-emitting diode having an omnidirectional reflector including a transparent conductive layer.
2. Description of the Related Art
LEDs have broad applications. For example, LEDs can be utilized in optical displays, traffic signs, data storage devices, communication devices, lighting devices, and medical devices. Therefore, the luminance and lighting efficiency of an LED has become an important consideration in LED production.
In Proc. SPIE Int. Soc. Opt. Eng. 4996 139 (2003) of Gessmann, an LED having an omnidirectional reflector and its producing method is disclosed. A GaN LED stack is formed on a sapphire substrate, an ITO transparent conductive layer is formed on the GaN LED stack, and an Ag layer is formed on the ITO transparent conductive layer. A GaN/ITO/Ag ODR-LED structure is therefore formed. The GaN/ITO/Ag ODR-LED structure can have a better light reflectivity than that of a prior art GaN LED structure having Ni—Au current distributing layers, thereby achieving good luminance. However, because the Ag layer cannot well bond to the ITO layer by cohesion, the GaN/ITO/Ag ODR-LED structure may suffer from peeling. In addition, because the reflectivity of the GaN/ITO/Ag ODR-LED relating to a short wavelength of blue light is low, the luminance of the GaN/ITO/Ag ODR-LED cannot efficiently be raised.
In a prior art GaN/ITO/Ag ODR-LED, a Cr layer is formed between the ITO layer and Ag layer in order to enhance the bonding between the ITO layer and Ag layer. However, because Cr has the characteristics of light absorption and low reflectivity, the luminance of the ODR-LED cannot be high.